New Delhi: After ‘severe’ pollution was observed for four days in Delhi, the air quality in the national capital slightly improved Wednesday, but was still in the ‘very poor’ category as weather conditions marginally favoured dispersion of pollutants, authorities said.

The Central Pollution Control Board (CPCB) data showed the overall air quality index (AQI) at the ‘very poor’ level of 378, while the Centre-run System of Air Quality and Weather Forecasting (SAFAR) showed an AQI of 364, which too falls in the ‘very poor’ category.

The overall PM2.5 level -- fine particulate matter in the air with a diameter of less than 2.5 micrometer -- was recorded at 220 and the PM10 level at 341 here, the CPCB said.

The national capital recorded its second highest pollution level of the year Sunday with an AQI of 450. The air quality remained ‘severe’ Monday and Tuesday before moving to the ‘very poor’ category Wednesday morning.

According to the Indian Institute of Tropical Meteorology (IITM), the air quality is likely to improve as weather conditions like the wind speed and the ventilation index are marginally favourable for dispersion of pollutants.

The ventilation index is the speed at which pollutants can get dispersed. A ventilation index lower than 6,000 sqm/second, with average wind speed less than 10 kmph, is unfavourable for dispersion of pollutants. The index was 5500 sqm/second Wednesday, the IITM said.

According to the SAFAR, the overall air quality over Delhi is ‘very poor’. “It will further improve a few notches by tomorrow as good wind speed will continue to disperse pollutants faster than that of accumulation due to colder condition and fog. The air quality will remain in the very poor range for the next three days. Moderate foggy conditions will prevail for the next two days over Delhi and surrounding regions and may not allow significant improvement," the SAFAR said.

In view of prevalence of ‘severe’ pollution in the national capital, industrial activities in pollution hotspots of Wazirpur, Mundka, Narela, Bawana, Sahibabad and Faridabad, and construction work across Delhi-NCR was ordered to remain shut till Wednesday.

The Environment Pollution Control Authority (EPCA) directed the traffic police to deploy special teams and ensure congestion-free traffic flow, particularly in identified high-traffic corridors. The agencies concerned have also been asked to ensure strict action against illegal industries, intensify ground action and make all efforts to control polluting activities, particularly waste burning.

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